There are a number of age related changes that can make it difficult for a man to maintain an erection and/or reach orgasm. Some changes can be treated with drugs and or therapies, but not all. Additionally, certain medications, particularly ACE inhibitors, a common medication to control blood pressure, impact a man's erectile function. If medications like Viagra are not improving your experience, I suggest speaking to your doctor about the symptoms you are experiencing.

Have been fitting a similar problem - even with viagra the erection stregth is eratic, even with twice the normal dosage.  My problem isn't related to medication.  I'm mid 50's, in outstanding physical condition, normal blood pressure, ran for 2 hours today and have the same interest in sex I have always had.  I notice I don't have the familiar morning erections any longer either.  Still enjoy the sex but when I am having a session  - any thing other than oral presents problems. As confidence erodes it makes it even worse.  I long for the days when I had a tent pole all the time!

sometime viagra will make it worse, therefore not opening your blood vessels at all..

are you taking it precisely one hour before.

I would also recommend that you see a physician, and engage in some form of exercise... as well as checking the weight issue?   and diet....
These are all factors at older ages influence the ability.... good luck.... but get checked out.

Your doc maybe able to to change your blood pressure medicine..lots of options these days. The BP meds are famous for causing this problem. 1)Check your pressure often. Make sure your not over medicated with BP drugs. 2) Check blood sugar for diabetes. Viagra often doesn't work so hot on diabetics. Levetra or Cialis may work better. Just got to test what works for you.

3)Run serum testosterone levels!!!!
At 58 your testosterone level probably half-normal or lower. Androderm will work wonders on how you feel and how your parts work (especially a males favorite one). Slight risks associated with the steroid don't equal the benefit. You will feel the results of normal testosterone levels immediately. Will put on muscle and feel better.

4) Routine heart check.If heart isn't working efficiently..hard to get pressure to your favorite friend.

Being around the same age..getting old is a bi**h aint it.

I also agree with Ciara, and Bizz.
However, there are natural alternatives. I would suggest that if you have an organic or natural supplement store, that you contact them. Most natural supplements have no side effects, but I would suggest consulting a physician before you take any enhancements, natural or otherwise.
TBM

Tie a stick to it

That works every time.

watch your blood sugar.  check for diabetes